IMPORTANCE OF ALKALINE BASES. * 107 



unites with it. By this is meant, that the quantities 

 in both cases must either be equal or multiples of 

 each other ; for the doctrine of equivalents denies 

 the possibility of their uniting in fractional parts. 

 This will be rendered obvious by a consideration of 

 the two following examples : 



100 parts of Cyanic Acid contain 23 26 oxygen = 1. 



100 parts of Cyanic Acid saturate 137-21 parts of potash, which contain 



23- 26 oxygen = 1 . 

 100 parts of Nitric Acid contain 73-85 oxygen = 5. 

 100 parts of Nitric Acid saturate 214-40 parts of oxide of silver, which 



contain 14 77 oxygen = 1. 



In the first of these cases, the relation of the 

 oxygen of the base to that of the acid is as 1 : 1 ; in 

 the second, as 1 : 5. The capacity for saturation 

 of each acid is, therefore, the constant quantity of 

 oxygen necessary to neutralize 100 parts of it. 



Many of the inorganic constituents vary accord- 

 ing to the soil in which the plants grow, but a cer- 

 tain number of them are indispensable to their de- 

 velopment. All substances in solution in a soil 

 are absorbed by the roots of plants, exactly as a 

 sponge imbibes a liquid, and all that it contains, 

 without selection. The substances thus conveyed 

 to plants are retained in greater or less quantity, or 

 are entirely separated when not suited for assimi- 

 lation. 



Phosphate of magnesia in combination with am- 

 monia is an invariable constituent of the seeds of 

 all kinds of grasses. It is contained in the outer 

 horny husk, and is introduced into bread along with 

 the flour, and also into beer. The bran of flour con- 

 tains the greatest quantity of it. It is this salt 

 which forms large crystalline concretions, often 

 amounting to several pounds in weight, in the cmcuni 

 of horses belonging to millers ; and when ammonia 

 is mixed with beer, the same salt separates as a 

 white precipitate. 



Most plants, perhaps all of them, contain organic 

 acids of very different composition and properties, 

 all of which are in combination with bases, such as 



